Ok, so E3B cannot license Poseidon; why can't the end user license it for themselves?
In our (german)
interview Christoph already linked to, it has been made clear that there will be no business relation between PCP and E3B anymore, including for example third parties sub-licensing the Deneb card.
Therefore also end users buying Deneb and Poseidon separately themselves would cause E3B earning money thanks to PCP. Thus the only solution could be finding a comparably high-skilled developer like Chris Hodges writing Deneb drivers for an AmigaOS-backported version of Poseidon for AROS.